One of the cities houses the headquarters of the Imperial Cartographic Society (for the betterment and enlightenment of the Empire). Probably just throw it into the city that has least interesting stuff going for it.Because Levitation spells won't last long enough for the cartographer to get to the required altitude then sketch all the details (plus the added inconvenience of them being without a desk to sit at as they work) The empire makes use of a modified glass bottomed Dwemeri Airship.

Just a little sidequest that offers the player a rewarding bit of eye candy with an interesting concept behind it and adds to the wonderment of the place. I guess we could script it up there to avoid players leviating up there outside of the quest. Or even better; script it so once a month it rises up stays for a few hours and then descendeds but without the quest being active you'll either be warned to leave and detained if you don't or outright detained for trespassing, that or you just can't get inside to the lower deck to stand on the glass "floor".

Because MGE would make it look stunning and it'd give the player a chance to appreciate the beauty of our exterior modders hard work. That and standing on a glass floor that high up is just too good to not do. Oh and Dwemeri airships don't get near enough attention, this one is modified to get it up there without the aid of the superior knowledge that the Dwarves possess/possessed. The imperials basically can get it high enough and keep it there for a few hours as long as it's stationary and then get it down again without it falling apart.

I don't have any other quest ideas for it really, just like the concept of it - anyone else feel free to throw in ideas - maybe even make something tragic happen up there - a bit of the main quest perhaps?

Possibly a nice idea for a quest - or even just a random feature in one city - but an entire joinable faction? I'm not so sure. There was a map recently released at the time of Oblivion, which is presumably in production at the time of MW. Perhaps you could somehow befriend Natalia Dravarel, the cartographer, and persuade her to take you up with her?